1. Field of the Invention
The present invention relates to metal working and, more particularly, to a fluting machine and method of producing fluted poles for lamp posts and other various applications by bending metal pipes.
2. Description of Related Art
For many years in our society, fluted poles have been used in the construction of lamp posts, as shown by reference numeral 11 in FIG. 1, because of their aesthetic ornamental appearance. Essentially, "flutes" are the indentations, or depressions, in the sides of a fluted pole 12. Fluted poles can take various configurations. They are generally tapered. They can possess a square or a circular cross section. They can be formed with differing numbers of flutes, for example, eight, twelve, sixteen, or thirty two flutes. Finally, the fluted poles can be constructed from soft metals, such as aluminum, or from stronger metals, such as a heavy gauge steel.
At first, fluted poles were made by grinding flutes, or indentations, into the outer circumference of a square or round pipe. This archaic rudimentary process was time consuming, to say the least. Flute uniformity was also lacking. Furthermore, the fluted poles were weak due to thickness variations in the fluted pole.
In 1906, a company known as Union Metal Corporation, located in Canton, Ohio, U.S.A., developed a method and apparatus for making fluted poles in a much faster and more efficient manner than in the past. The apparatus bent pipe into a fluted configuration by using hydraulic technology, which was in a state of infancy at the time. At present, Union Metal has been making fluted poles in this manner for over eighty years.
Essentially, the Union Metal apparatus has a mandrel for supporting a pipe to be converted into a fluted pole. The mandrel is moved longitudinally through a head via a hydraulic cylinder attached to one end of the mandrel. The head has eight hydraulic cylinders which basically press a set of eight roller-like, V-shaped dies within an opening at the center of the head through which the mandrel is passed. The eight dies are situated symmetrically around the head opening so as to create a symmetric fluted pole.
In operation, the dies are extended into the head opening. Next, the mandrel is forced by its associated hydraulic cylinder to carry a pipe through the head opening, while the dies bend flutes into the pipe to thereby form a fluted pole. In order to remove the fluted pole from the mandrel, the fluted pole is generally pulled off of the mandrel. In order to facilitate removal, the mandrel is often oiled with a heavy black oil. A heavy brace is positioned in front of the mandrel. Then, a ring is placed around the back end of the mandrel and is pulled forward so as to pull the fluted pole from the mandrel. A mandrel vibrator is sometimes employed to aid in separating the fluted pole from the mandrel.
Although very innovative for its time, the Union Metal apparatus and associated methodology suffers from various design and implementation problems. First, the process is very slow. Only 5 or 6 fluted poles can be manufactured in an hour.
During the removal process, the fluted poles are often destroyed in whole or in part. It is common for 3 to 4 feet of a pole to be torn by the removal apparatus.
The hydraulic systems of the Union Metal apparatus contribute other even more fundamental problems. The hydraulic systems have many operational variables which lead to inaccurate control and varying fluted pole quality. For instance, the hydraulic cylinders in the head do not maintain equal die pressures around the circumference of the mandrel. As a result, the pipe bends too much or too little, is bowed, and/or is difficult to remove from the mandrel. Also, after continued operation, the mandrel eventually progresses to the bottom of the head. Consequently, the hydraulic feed to the die cylinders must be re-adjusted very often.
The hydraulic cylinders in the head must be overhauled frequently. Thus, the heads are designed to be interchangeable so that while one head is being overhauled, another can be in operation.
When the mandrel hydraulic cylinder carries a pipe through the head opening, the mandrel hydraulic cylinder does not maintain a constant drive speed, because of varying resistances against the drive force. The varying resistances are caused by the varying metallurgical characteristics of the pipe. In other words, some areas of the pipe are hard, while other areas are soft, or more malleable.
Because of the mandrel hydraulic cylinder design, the pipes can be bent only in one driving direction. In order to pass the mandrel with a pipe through the head a second time, if necessary, the dies must be retracted so that the mandrel hydraulic cylinder can be pulled back to its starting position behind the head.
Finally, because of the rudimentary design of the hydraulic die cylinders, every time a pipe material changes, all of the hydraulic settings must be reconfigured. For example, if the Union Metal apparatus were being converted from working on heavy steel pipes to working on aluminum pipes, then the hydraulic die cylinders need to be fed less hydraulic pressure so as to compensate for the softer metal. This reconfiguration process is time consuming and is undesirably imprecise.